Eddy current deceleration device

ABSTRACT

An eddy current deceleration device comprises: a rotor mounted on a rotary shaft; a first magnet ring arranged facing this rotor and including permanent magnets that are arranged at prescribed intervals in the circumferential direction and such that the poles thereof facing each other in the circumferential direction are of a same polarity, and magnetic members interposed between these permanent magnets; and a second magnet ring arranged between this first magnet ring and the rotor and including permanent magnets and magnetic members which are similar to those of the first magnet ring; at least one of the first and second magnet rings being freely rotatable. The permanent magnets of the first and second magnet rings can be magnetized separately between the first and second magnet rings. This means that the permanent magnets of length half of the length of the permanent magnet pairs are magnetized, so even though the intervals between adjacent permanent magnets in the circumferential direction are made smaller, ample magnetization can still be achieved. Also, the braking force exhibited by the permanent magnets is that of the length of the sets of pairs of permanent magnets. Consequently, the braking force can be increased.

REFERENCE TO RELATED APPLICATION

[0001] The present invention claims priority from Japanese PatentApplication 2002-154349 filed in Japan on May 28, 2002 and JapanesePatent Application No. 2002-187293 filed in Japan on Jun. 27, 2002. Thecontent of these Japanese applications is hereby incorporated in thespecification of the present application by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an eddy current decelerationdevice that applies deceleration braking to a vehicle.

[0004] 2. Description of the Related Art

[0005] The present inventor has previously developed an eddy currentdeceleration device as shown in FIG. 34 to FIG. 36. As shown in theseFigures, this eddy current deceleration device a comprises a drum-shapedrotor c that is mounted on a power transmission system such as a driveshaft b of a vehicle and a stator d (source of magnetic force) mountedon a fixed system such as a vehicle transmission. The vehicle isdecelerated and braked by generating eddy currents in the rotor c bysupplying magnetism from the stator d to the rotor c. The decelerationbraking is released by shielding the magnetism within the stator d.

[0006] The stator d comprises a hollow ring-shaped casing e that issupported on a fixed system, a magnetic ring g that is freely rotatablyaccommodated, by means of a bush f, in the interior of the casing e andan actuator (cylinder h or the like) that rotates the magnetic ring g.As shown in FIG. 35 and FIG. 36, the magnetic ring g comprises a supportring i made of a non-magnetic body, a plurality of permanent magnets jmounted with a prescribed spacing in the circumferential direction onthe support ring i and magnetic members k interposed between each of thepermanent magnets j. These permanent magnets j have magnetic pole facesat the respective opposite end faces in the circumferential directionand are arranged such that facing poles thereof in the circumferentialdirection are of the same polarity. In addition, on the casing e, thereare alternately arranged along the circumferential direction pole pieces1 made of magnetic material (soft magnetic material) positioned in aregion between the magnetic ring g and the rotor c and supports m madeof non-magnetic material that support these pole pieces. As shown inFIG. 36, the circumferential length of the pole pieces 1 matches thecircumferential length of the magnetic members k.

[0007] With this construction, as shown in FIG. 35, when the permanentmagnets j are positioned below the pole pieces 1 by rotating themagnetic ring g with the cylinder h, the magnetism of the permanentmagnets j is shielded by the pole pieces 1, constituting a short-circuitn, so no eddy current is generated in the rotor c and no decelerationbraking is produced in the vehicle. In contrast, as shown in FIG. 36,when the magnetic members k are positioned below the pole pieces 1, amagnetic circuit o linking the N pole and S pole is constituted betweenthe permanent magnet j and the rotor c, so eddy current is generated inthe rotor c, producing deceleration braking of the vehicle.

[0008] In order to increase the braking force in such an eddy currentdeceleration device a, it is important to intensify the magnetic forceof the permanent magnets j of the magnetic ring g. However, as shown inFIG. 35 and FIG. 36, if the permanent magnets j are arranged with facingmagnetic poles in the circumferential direction thereof being of thesame polarity, when the permanent magnets j are magnetized afterassembly of the permanent magnets j and magnetic members k in ringfashion, sufficient magnetization of the permanent magnets j cannot beachieved unless the circumferential length of the pole pieces kinterposed between these permanent magnets j is expanded to a certainextent. Consequently, if magnetization of the permanent magnets j isprioritized, the gaps between the permanent magnets j have to be widenedto a certain extent, thereby restricting the number of permanent magnetsj that can be provided. On the other hand, if the number of permanentmagnets j that are to be provided is prioritized, magnetization becomesinsufficient because the gap therebetween is reduced. It was thereforedifficult to increase the braking force.

[0009] Also, as shown in FIG. 35, although, when the decelerationbraking is turned off, a dominant part of the magnetism of the permanentmagnets j is shielded within the casing e by the pole pieces 1, someportion thereof leaks to the rotor c through the supports m made ofnon-magnetic material, thereby constituting a magnetic leakage circuitp. Weak eddy currents are thereby generated in the rotor c, giving riseto dragging braking, which has an adverse effect on fuel consumption ofthe vehicle.

[0010] Related prior art is disclosed in for example Japanese PatentPublication Nos. H. 6-83570, H. 6-83571, and H. 7-118901, and JapaneseLaid-open Patent Application Nos. 2000-350432 and 2001-8436.

[0011] An object of the present invention, which was created in view ofthe above, is to provide an eddy current deceleration device whereinbraking force can be increased and dragging braking prevented.

SUMMARY OF THE INVENTION

[0012] The invention according to claim 1 of the present applicationconsists in an eddy current deceleration device comprising: a rotormounted on a rotary shaft; a first magnet ring arranged facing thisrotor and comprising a plurality of permanent magnets that are arrangedwith a prescribed spacing in the circumferential direction and such thatthe poles thereof facing in the circumferential direction are of a samepolarity, and magnetic members interposed between these permanentmagnets; and a second magnet ring arranged between this first magnetring and the rotor and comprising permanent magnets and magnetic memberssimilar to those of the first magnet ring; at least one of the first andsecond magnet rings being freely rotatable.

[0013] According to the present invention, when at least one of thefirst and second magnet rings is rotated, putting these magnet rings ina phase in which the permanent magnets of the first magnet ring and thepermanent magnets of the second magnet ring are arranged with theiridentical polarity poles, a magnetic circuit is constituted by thepermanent magnets and the rotor, causing eddy currents to be generatedin the rotor and thereby producing deceleration braking of the vehicle.Contrariwise, when these rings are put in a phase in which the permanentmagnets of the first magnet ring and the permanent magnets of the secondmagnet ring are arranged with their opposite polarity poles, a screeningmagnetic circuit is constituted whereby the permanent magnets of thefirst magnet ring and the permanent magnets of the second magnet ringare mutually magnetically short-circuited, with the result that no eddycurrents are generated in the rotor and deceleration braking isreleased.

[0014] Also, during braking, the respective permanent magnets of thefirst and second magnet rings are in a condition in which two permanentmagnets are adjacent with the same polarity, so these permanent magnetsconstitute sets of pairs, which exhibit strong magnetic force. Also, therespective permanent magnets of the first and second magnet rings can beseparately magnetized in the first magnet ring and the second magnetring. When this is done, as already described, magnetization of thepermanent magnets is achieved with these being of a length that is halfthe length of the sets of pairs, so the intervals between adjacentpermanent magnets in the circumferential direction can be made small yetample magnetization can still be achieved. Braking force is therebyimproved.

[0015] The invention according to claim 2 consists in an eddy currentdeceleration device comprising: a rotor mounted on a rotary shaft; amagnet ring arranged facing this rotor and comprising a plurality ofpermanent magnets that are arranged at a prescribed pitch in thecircumferential direction and such that the polarities of their polesfacing the rotor are alternately inverted, and magnetic members forconnecting the magnetic poles, of these permanent magnets, that face theopposite side of the rotor; and a magnetic ring arranged between thismagnet ring and the rotor and comprising a plurality of permanentmagnets that are arranged at a prescribed pitch in the circumferentialdirection and such that the poles thereof facing in the circumferentialdirection are of a same polarity, and magnetic members that hold thesepermanent magnets; at least one of the magnet ring and magnetic ringbeing freely rotatable.

[0016] According to the present invention, by rotating at least one ofthe magnet ring and magnetic ring so as to put these rings in a phasesuch that permanent magnets, of the permanent magnets of the magnetring, that are of the same polarity as the permanent magnets sandwichingthe magnetic members, face the magnetic members between the permanentmagnets of the magnetic ring, the magnetism that is generated from thepermanent magnets of the magnetic ring and the magnet ring can berespectively transmitted to the rotor, making it possible to performstrong deceleration braking of the rotary shaft with a high magneticflux density.

[0017] Contrariwise, by putting these rings in a phase in whichpermanent magnets, of the permanent magnets of the magnet ring, that areof unsame polarity to the permanent magnets that sandwich the magneticmembers face the magnetic members between the permanent magnets of themagnetic ring, the permanent magnets of the magnet ring and the magneticring can be mutually magnetically short-circuited, thereby making itpossible to prevent magnetic leakage to the rotor and so preventdragging torque from being generated.

[0018] The invention according to claim 3 consists in an eddy currentdeceleration device wherein the rotor comprises a drum body fixed to therotary shaft.

[0019] The invention according to claim 4 consists in an eddy currentdeceleration device wherein the rotor comprises a disk body fixed to therotary shaft.

[0020] The invention according to claim 5 comprises an actuator thatrotates at least one of the magnet ring and magnetic ring and that setsthe relative position of the magnet ring and magnetic ring in one of abraking position, in which permanent magnets of the permanent magnets ofthe magnet ring that are of the same polarity as the permanent magnetssandwiching the magnetic members are directed towards magnetic membersbetween the permanent magnets of the magnetic ring, and a non-brakingposition in which the magnet ring and the magnetic ring are offset by aprescribed rotational width exceeding ½ pitch but less than 1 pitch inthe circumferential direction from this braking position.

[0021] According to the present invention, the permanent magnets of themagnetic ring can be made smaller and of weaker magnetic force than thepermanent magnets of the magnet ring, so the thickness of the magneticring in the radial direction can be reduced.

[0022] According to the invention of claim 6, the non-braking positionis set in a position offset by substantially ⅔ pitch in thecircumferential direction from the braking position.

[0023] According to the invention of claim 7, the magnetic ringcomprises a plurality of magnetic blocks formed in arcuate shape andconnecting elements that connect the ends in the circumferentialdirection of these magnetic blocks, while holding the permanent magnets.

[0024] According to the invention of claim 8, a magnetic member of themagnetic ring is formed in annular shape and is provided with embeddingholes so that the permanent magnets are embedded and fixed in theseholes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a side cross-sectional view of an eddy currentdeceleration device according to an embodiment of the inventionaccording to claim 1;

[0026]FIG. 2 is a front cross-sectional view of the brake-OFF conditionof the above device;

[0027]FIG. 3 is a front cross-sectional view of the brake-ON conditionof the above device;

[0028]FIG. 4 is a front cross-sectional view of a second magnetic ringof the above device;

[0029]FIG. 5 is a cross-sectional view along the line V-V of FIG. 4;

[0030]FIG. 6 is a front cross-sectional view of a first magnetic ring ofthe above device;

[0031]FIG. 7 is a cross-sectional view along the line VII-VII of FIG. 4;

[0032]FIG. 8 is a front cross-sectional view of an eddy currentdeceleration device (brake-ON condition) according to an embodiment ofthe invention according to claim 2;

[0033]FIG. 9 is a front cross-sectional view of the above device(brake-OFF condition);

[0034]FIG. 10(a) is a front cross-sectional view showing a modifiedexample of a magnetic ring of the above device;

[0035]FIG. 10(b) is a front cross-sectional view showing a modifiedexample of the above magnetic ring;

[0036]FIG. 10(c) is a front cross-sectional view showing a modifiedexample of the above magnetic ring;

[0037]FIG. 11(d) is a front cross-sectional view showing a furthermodified example of the above magnetic ring;

[0038]FIG. 11(e) is a front cross-sectional view showing a furthermodified example of the above magnetic ring;

[0039]FIG. 11(f) is a front cross-sectional view showing a furthermodified example of the above magnetic ring;

[0040]FIG. 12 is a front cross-sectional view of an eddy currentdeceleration device (brake-ON condition) according to a furtherembodiment of the invention according to claim 2;

[0041]FIG. 13 is a front cross-sectional view of the above eddy currentdeceleration device (brake-OFF condition);

[0042]FIG. 14 is a front cross-sectional view showing a modified exampleof a magnetic ring of the above device;

[0043]FIG. 15 is a front cross-sectional view (brake-ON condition) of aneddy current deceleration device comprising a further modified exampleof the above magnetic ring;

[0044]FIG. 16 is a front cross-sectional view of the above eddy currentdeceleration device (weak braking force condition);

[0045]FIG. 17 is a front cross-sectional view of the above eddy currentdeceleration device (brake-OFF condition);

[0046]FIG. 18(a) is a plan cross-sectional view of an eddy currentdeceleration device (brake-OFF condition) according to an embodiment inwhich the above rotor is of the disk type;

[0047]FIG. 18(b) is a side cross-sectional view of the above eddycurrent deceleration device;

[0048]FIG. 19 is a plan cross-sectional view of the brake-ON conditionof the above device;

[0049]FIG. 20(a) is a plan cross-sectional view of an eddy currentdeceleration device (brake-OFF condition) according to an embodiment inwhich the above rotor is of the twin disk type;

[0050]FIG. 20(b) is a side cross-sectional view of the above eddycurrent deceleration device;

[0051]FIG. 21 is a plan cross-sectional view of the brake-ON conditionof the above device;

[0052]FIG. 22 is a plan cross-sectional view showing a modified exampleof the first magnetic ring of the above device (brake-OFF condition);

[0053]FIG. 23 is a plan cross-sectional view of the brake-ON conditionof the above device;

[0054]FIG. 24 is a front cross-sectional view of an eddy currentdeceleration device in the brake-ON condition showing an embodiment of adevice according to claim 5;

[0055]FIG. 25 is a front cross-sectional view of an eddy currentdeceleration device according to FIG. 24 in the brake-OFF condition;

[0056]FIG. 26 is a side cross-sectional view of the above eddy currentdeceleration device;

[0057]FIG. 27 is a front cross-sectional view of an eddy currentdeceleration device in the brake-ON condition illustrating anotherembodiment;

[0058]FIG. 28 is a front cross-sectional view of an eddy currentdeceleration device according to FIG. 27 in the brake-OFF condition;

[0059]FIG. 29 is a front cross-sectional view showing a modified exampleof a magnetic ring of an eddy current deceleration device;

[0060]FIG. 30 is a front cross-sectional view showing a modified exampleof a magnetic ring of an eddy current deceleration device;

[0061]FIG. 31 is a front cross-sectional view showing a modified exampleof a magnetic ring of an eddy current deceleration device;

[0062]FIG. 32 is a side cross-sectional view showing a modified exampleof the above eddy current deceleration device;

[0063]FIG. 33 is a side cross-sectional view showing a modified exampleof the above eddy current deceleration device;

[0064]FIG. 34 is a side cross-sectional view of an eddy currentdeceleration device previously developed by the present inventors;

[0065]FIG. 35 is a front cross-sectional view of the above device in thebrake-OFF condition; and

[0066]FIG. 36 is a front cross-sectional view of the above device in thebrake-ON condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] An embodiment of the present invention according to claim 1 isdescribed with reference to the appended drawings.

[0068]FIG. 1 shows a side cross-sectional view of an eddy currentdeceleration device according to an embodiment of the invention. FIG. 2shows a front cross-sectional view of the brake-OFF condition of thisdevice. FIG. 3 shows a front cross-sectional view of the brake-ONcondition of this device.

[0069] As shown in FIG. 1, this eddy current deceleration device 1comprises a drum-shaped rotor 3 that is mounted on a rotary shaft 2 ofthe power transmission system of a vehicle and a stator 4 (source ofmagnetic force) mounted on a fixed system such as the vehicletransmission. This eddy current deceleration device is capable ofdeceleration braking of the vehicle by generating eddy currents in therotor 3 by supplying magnetism to the rotor 3 from the stator 4 and ofreleasing the deceleration braking by shielding the magnetism within thestator 4.

[0070] The stator 4 comprises a hollow ring-shaped casing 5 supported bythe fixed system, a first magnet ring 7 freely rotatably accommodated bymeans of a bush 6 in the interior of the casing 5 and an actuator (fluidcylinder 8 or the like) that rotates the first magnet ring 7. As shownin FIG. 2 and FIG. 3, the first magnet ring 7 comprises a support ring 9made of a non-magnetic body (such as austenitic stainless steel), aplurality of permanent magnets 10 mounted with a prescribed spacing inthe circumferential direction of the support ring 9 and magnetic members11 (for example laminated bodies made of electromagnetic steel sheet orblock members made of iron) interposed between these permanent magnets10. The permanent magnets 10 are provided with magnetic pole faces atopposite end faces in the circumferential direction, and the facingpoles thereof in the circumferential direction have the same polarity.

[0071] As shown in FIG. 6 and FIG. 7, the first magnet ring 7 isconstituted for example by fixing a block-shaped magnetic member 11having claws 12 at the opposite ends thereof in the circumferentialdirection on the outer circumferential side on the outer circumferentialsurface of a support ring 9 made of a non-magnetic body by means ofbolts, screws or other fixing elements 13, such that the permanentmagnets 10 are secured in position by the aforementioned claws 12between the magnetic members 11. In addition, rigidity may be increasedby attaching connecting plates 14 formed in sector shape or ring shapealong the circumferential direction on both sides of the magneticmembers 11 by means of bolts, screws or other fixing elements 15. Theconnecting plates 14 are made of non-magnetic bodies in order not tomagnetically short-circuit the adjacent permanent magnets 10.

[0072] As shown in FIG. 1 to FIG. 3, a second magnet ring 18 comprisingpermanent magnets 16 and magnetic members 17 similar to the firstmagnetic ring 7 is integrally provided, positioned in a region betweenthe first magnet ring 7 and the rotor 3 in the casing 5. Specifically,the second magnet ring 18 comprises a plurality of permanent magnets 16mounted with a prescribed spacing in the circumferential direction andarranged with facing magnetic poles thereof in the circumferentialdirection being of the same polarity, and magnetic members 17 (forexample consisting of a laminated body of electromagnetic sheet steel ora block member made of iron) interposed between the permanent magnets16. The pitch and circumferential length of the permanent magnets 10, 16and magnetic members 11, 17 of the internal and external magnet rings 7,18 are set to be substantially equal on the inside and the outside. Themagnetic members 11, 17 constitute respective pole pieces of the innerand outer permanent magnets 10, 16.

[0073] The second magnet ring 18, for example as shown in FIG. 4 andFIG. 5, is constituted in ring shape by connecting block-shaped magneticmembers or laminated bodies 17 made of electromagnetic sheet steelhaving recesses 19 at the opposite ends thereof in the circumferentialdirection on the outer circumferential side by means of connectingelements 21 that are fixed by means of bolts, screws or other fixingelements 20 in the recesses 19, on both sides of the permanent magnets16. In addition, rigidity may be increased by attaching connectingplates 22 formed in sector shape or ring shape along the circumferentialdirection on both sides of the magnetic members 17 by means of bolts,screws or other fixing elements 23. These connecting plates 22 andconnecting elements 21 are made of non-magnetic bodies in order not tomagnetically short-circuit the adjacent permanent magnets 16. Theconnecting elements 21 could also be made of soft magnetic material(iron material) in order to prevent magnetic leakage to the rotor 3.

[0074] The operation of this embodiment will now be described.

[0075] When deceleration braking of this eddy current decelerationdevice is turned off, as shown in FIG. 2, the permanent magnets 10 ofthe first magnet ring 7 and the permanent magnets 16 of the secondmagnet ring 18 are put in a phase where opposite polarity poles areadjacent to each other by rotating the first magnet ring 7 using thecylinder 8. When this is done, a shielding magnetic circuit 24 isconstituted by mutual magnetic short-circuiting of the permanent magnets10 of the first magnet ring 7 and the permanent magnets 16 of the secondmagnet ring 18. Eddy currents are therefore not generated in the rotor3, so deceleration braking does not occur. That is, in this condition,the magnetic members 11 of the first magnet ring 7 and the magneticmembers 17 of the second magnet ring 18 opposite this first magnet ringconstitute pole pieces of mutually opposite polarities (N pole or Spole), so the permanent magnets 10, 16 are mutually magneticallyshort-circuited through the pole pieces 11, 17.

[0076] In contrast, when deceleration braking is turned on, as shown inFIG. 3, the permanent magnets 10 of the first magnet ring 7 and thepermanent magnets 16 of the second magnet ring 18 are put in a phasewhere identical polarity poles are adjacent to each other, by rotatingthe first magnet ring 7. When this is done, magnetic circuits 25, 26 areconstituted by the permanent magnets 10 and 16 in the first and secondmagnet rings 7 and 18 and the rotor 3. Eddy currents are thereforegenerated in the rotor 3, causing deceleration braking of the vehicle.Specifically, the magnetic member 11 of the first magnet ring 7 and themagnetic member 17 of the second magnet ring 18 facing this first magnetring then constitute pole pieces of same polarity (N pole/N pole or Spole/S pole), so these permanent magnets 10, 16 are respectivelymagnetically connected through the rotor 3, without mutual magneticshort-circuiting through the pole pieces 11, 17.

[0077] Furthermore, during deceleration braking as illustrated in FIG.3, since the respective permanent magnets 10, 16 of the first and secondmagnet rings 7, 18 are arranged in pairs in the radial direction withtheir pole surfaces in the circumferential direction being of identicalpolarity, each pair of permanent magnets provides intense magneticforce. Strong braking force is thereby obtained by a magnetic force frompermanent magnets 10, 16 of substantially double length. Also, thepermanent magnets 10, 16 of the first magnet ring 7 and second magnetring 18 can be magnetized separately between the first and second magnetrings 7 and 18. When this separate magnetization is performed, half thelength of the magnet pair described above is magnetized, and,consequently, even if the distance between adjacent permanent magnets 10and 10 or 16 and 16 in the circumferential direction is reduced, amplemagnetization can still be achieved after assembly into the form of aring. Braking force is therefore improved.

[0078] Specifically, with this embodiment, since the respectivepermanent magnets 10, 16 of the first and second magnet rings 7 and 18are of length half the length of the magnet pair which is constituted byarranging two such magnets are arranged to exhibit braking force, evenif the spacing of the magnets 10, 16 in the circumferential direction isset to be small, ample magnetization can be achieved through therespective pole pieces 11, 17 after assembly in ring form. Furthermore,during braking, braking force is increased, since sets of pairs of innerand outer permanent magnets 10 and 16 are constituted, functioning aspermanent magnets of substantially double length.

[0079] The reason why, in FIG. 2, the magnetic members 17 of the secondmagnet ring 18 project towards the rotor 3 and a portion of thepermanent magnets 16 is recessed is in order to reduce magnetic leakageto the rotor 3 by projection of the magnetic members 17 and in order toreduce the influence on the permanent magnets 16 of the heat of therotor 3 generated by the eddy currents, by recessing a portion of thepermanent magnets 16.

[0080] Next, an embodiment of the invention to according to claim 2 willbe described with reference to FIG. 8 and FIG. 9.

[0081]FIG. 8 shows a front cross-sectional view of the brake-ONcondition of an eddy current deceleration device according to anembodiment of the invention. FIG. 9 shows a front cross-sectional viewof the brake-OFF condition of this device.

[0082] As shown in these Figures, an eddy current deceleration device 1a according to this embodiment is of substantially the same constructionas an eddy current deceleration device 1 according to the previousembodiment, differing only in that a magnetic ring 27 is provided inplace of the aforementioned second magnet ring 18 in the casing 5 of thestator 4. Identical components are therefore given the same referencesymbols and further description thereof is omitted, only the aspectsthat are different being described. Also, the first magnet ring 7 of theprevious embodiment is referred to in this embodiment simply as magnetring 7.

[0083] The magnetic ring 27 is provided in the casing 5 positioned in aregion between the magnet ring 7 and the rotor 3. The magnetic ring 27comprises an annular body 28 made of a magnetic body (soft magneticmember such as an iron block or laminated electromagnetic steel sheet)and a plurality of permanent magnets 29 embedded with a prescribedspacing in the circumferential direction in the interior of the annularbody 28. The permanent magnets 29 are provided with pole faces at bothend faces thereof in the circumferential direction and are arranged sothat facing poles in the circumferential direction are of same polarity.

[0084] In the magnetic ring 27, as shown in FIG. 10(a), a raised portion30 may be formed between the permanent magnets 29, or, as shown in FIG.10(b), the raised portion 30 may be absent. Also, as shown in FIG.10(c), the permanent magnets 29 may be fitted into recessed portionsformed in the annular body 28 made of a magnetic body and metal elements31 made of a magnetic member (soft magnetic body such as electromagneticsteel sheet) may be fixed and mounted in the annular body 28 by means ofbolts, screws or other fixing elements 32. Non-magnetic material(stainless steel or the like) may be employed for the metal elements 31.

[0085] Also, as shown in FIG. 11(d), the magnetic ring 27 may beconstituted in ring shape by connecting blocks 33 made of magneticbodies (soft magnetic members such as iron blocks or laminatedelectromagnetic steel sheet) by metal elements 35 fixed by bolts, screwsor other fixing elements 34, with the permanent magnets 29 sandwichedtherebetween. The metallic elements 35 are made of magnetic members(soft magnetic bodies such as electromagnetic steel sheet) ornon-magnetic material (stainless steel or the like) could also beemployed. As shown in FIG. 11(e) and FIG. 11(f), the permanent magnets29 may be embedded in holes formed in the electromagnetic sheet steel 28laminated in the thickness direction of the drawing sheet.

[0086] Essentially, the magnetic ring 27 may be constituted with aplurality of permanent magnets 29 embedded in an annular body 28 made ofmagnetic material, with prescribed spacing in the circumferentialdirection. Also, as shown in FIG. 8 to FIG. 10(c), the permanent magnets29 comprise two pole faces at both end faces thereof in thecircumferential direction and arranged such that the facing poles in thecircumferential direction are of same polarity. Also, as shown in FIG.8, the pitch in the circumferential direction of the permanent magnets29 of the magnetic ring 27 is set to be substantially equal to the pitchof the permanent magnets 10 of the magnet ring 7 positioned on theinside thereof.

[0087] The operation of this embodiment constructed as above will now bedescribed.

[0088] As shown in FIG. 8, when deceleration braking is turned on, thepermanent magnets 10 of the magnet ring 7 and the permanent magnets 29of the magnet ring 27 are put in a phase where identical polarity polesare adjacent to each other, by rotating the magnet ring 7 using thecylinder 8. When this is done, magnetic circuits 36, 37 are constitutedby the permanent magnets 10 and 29 in the magnet ring 7 and magneticring 27 and the rotor 3.

[0089] The N poles and S poles of the permanent magnets 29 embedded inthe magnetic ring 27 are then short-circuited 38 by the magnetic bodiesat the outer circumference and inner circumference of the magnetic ring27, with the result that the vicinity thereof is magnetically saturated.All of the magnetism of the permanent magnets 10 of the magnet ring 7therefore goes to constituting the magnetic circuit 36 through the rotor3, with no magnetic shielding (broken line 39) by the magnetic ring 27by escaping in the circumferential direction through the vicinity of themagnetically saturated permanent magnets 29 of the magnetic ring 27.Eddy currents are therefore generated in the rotor 3, producingdeceleration braking of the vehicle.

[0090] In contrast, when deceleration braking is turned off, as shown inFIG. 9, the permanent magnets 10 of the magnet ring 7 and the permanentmagnets 29 of the magnetic ring 27 are put into a condition in whichthey are offset by ½ pitch to 1 pitch, by rotating the magnet ring 7. InFIG. 9, x represents ½ pitch. That is, the magnetism of the permanentmagnets 10 of the magnet ring 7 is shielded by the magnetic ring 27.Specifically, part of the magnetism of the permanent magnets 10 of themagnet ring 7 is shielded by short-circuiting 40 through the magneticbodies (annular bodies 28) between the permanent magnets 29, 29 of themagnetic ring 27 while the remainder thereof is shielded byshort-circuiting 41 through the permanent magnets 29 of the magneticring 27. No eddy currents are therefore generated in the rotor 3 anddeceleration braking is released.

[0091] Even when this braking is released, the permanent magnets 29embedded in the magnetic ring 27 still produce magnetic saturation ofthe part of the magnetic ring 27 in their vicinity. Consequently,leakage of the magnetism of the permanent magnets 10 of the magnet ring7 towards the rotor 3 passing through this magnetically saturated partin the radial direction is prevented. Dragging braking is therebyprevented. Also, since the permanent magnets embedded in the magneticring 27 are magnetically short-circuited by the interior of the magneticring 27, leakage of magnetism towards the rotor 3 is suppressed. Forthis reason also, dragging braking can be prevented.

[0092] Also, since the permanent magnets 10 of the magnet ring 7 and thepermanent magnets 29 of the magnetic ring 27 are offset by a pitch thatis slightly different from ½ pitch, rather than being exactly offset by½ pitch, the magnetism of the permanent magnets 10 of the magnet ring 7is short-circuited 41 with the permanent magnets 29 on the side closestto the magnetic ring 27. In this way, leakage of magnetism towards therotor 3 can be prevented. Specifically, if the permanent magnets were tobe offset by exactly ½ pitch, the shielding circuit 41 shown in FIG. 9would be difficult to create, so leakage of magnetism is totally avoidedby positively forming a shielding circuit 41 by offsetting by about ⅓pitch (or slightly more or less than ½ pitch).

[0093] Also, compared with offsetting by 1 pitch, since the angle ofrotation (sliding distance) of the magnet ring 7 can be made small, theactuator (cylinder 8) can be made of small size, enabling compactness ofthe device as a whole to be promoted. It should be noted that it wouldbe possible to turn the braking force off even by offsetting thepermanent magnets 10 of the magnet ring 7 and of the permanent magnets29 of the magnetic ring 27 by 1 pitch, with the permanent magnets in aphase in which opposite polarity poles are mutually adjacent, in thesame way as in case of the embodiment of FIG. 2. However, in this case,the angle of rotation (sliding distance) of the magnet ring 7 becomeslarge.

[0094] Preferably, the pitch of offset of the magnet ring 7 in thedirection of rotation is 1 pitch when the amount of magnetic flux of themagnetic ring 27 and the amount of magnetic flux of the magnet ring 7are substantially the same and is less than 1 pitch when the amount ofmagnetic flux of the magnetic ring 27 is smaller than the amount ofmagnetic flux of the magnet ring 7 (when the size of the magnets 27 issmall).

[0095] A further embodiment is illustrated in FIG. 12 and FIG. 13.

[0096] As illustrated, in this embodiment (eddy current decelerationdevice 1 x), only the construction of the magnet ring 7 of theembodiment shown in FIG. 8 is altered; the rest of the construction isthe same. The magnet ring 7 x of this embodiment comprises a supportring 9 x made of a magnetic body, a plurality of permanent magnets 10 xmounted with a prescribed spacing in the circumferential direction atthe outer circumferential surface of the support ring 9 x and anon-magnetic body (bolt or screw or the like fixing element 11 x used tofix the magnets) interposed between the permanent magnets 10 x.

[0097] The permanent magnets 10 x have magnetic poles on the outside endface and inside end face in the radial direction and are arranged withmagnets that are adjacent in the circumferential direction being ofopposite polarity. As in the example illustrated, if fixed metalelements 12 x made of a non-magnetic body formed with the same length asthe magnets 10 x in the axial direction are interposed between thepermanent magnets 10 x, magnetic bodies may be employed for screws orthe like 11 x used to fix these permanent magnets.

[0098] With this construction, deceleration braking is turned on byrotating the magnet ring 7 x as shown in FIG. 12 so that the permanentmagnets 10 x of the magnet ring 7 x and the rotor 3 are magneticallyconnected by the magnetic circuit 25 x and the permanent magnets 29 ofthe magnetic ring 27 and the rotor 3 are magnetically connected by themagnetic circuit 26 x. In contrast, deceleration braking is released byrotating the magnet ring 7 x as shown in FIG. 13 so that the permanentmagnets 10 x of the magnet ring 7 x and the permanent magnets 29 of themagnetic ring 27 are magnetically short-circuited.

[0099] Alternatively, the magnet ring 7 x of this embodiment may be of aconstruction 7 y as shown in FIG. 14. The magnet ring 7 y in FIG. 14comprises permanent magnets 10 y integrally embedded in a ring 9 y madeof a magnetic body with cavities (holes) 11 y constituted bymagnetically insulating bodies formed between the permanent magnets 10y. The same beneficial action as in the case of FIG. 12 and FIG. 13 maybe obtained using this magnet ring 7 y.

[0100] Alternatively, the magnet ring 7 y may have a construction 7 z asshown in FIG. 15. This magnet ring 7 z comprises sets of pairs ofpermanent magnets 10 z arranged in hill/valley fashion integrallyembedded in a ring 9 z made of a magnetic body and is formed withcavities (holes) 11 z act as magnetically insulating bodies between thepermanent magnets 10 z.

[0101] Employing such a magnet ring 7 z, deceleration braking is turnedon by magnetically connecting the permanent magnets 10 z of the magnetring 7 z and the rotor 3 by rotating the magnet ring 7 z as shown inFIG. 15. It should be noted that, in fact, preferably the permanentmagnets 10 z are made thicker than illustrated and the cavities 11 z aremade larger than illustrated. This is in order to obtain strong magneticforce and a high degree of magnetic insulation.

[0102] If the magnet ring 7 z is rotated as shown in FIG. 16, thepermanent magnets 10 z of the magnet ring 7 z are magnetically shieldedby the magnetic ring 27, so the magnetism of the magnet ring 7 z is notconnected with the rotor 3 and only the magnetism of the permanentmagnets 29 of the magnetic ring 27 is connected with the rotor 3. Thebraking force is thereby attenuated. That is, the thickness of themagnetic body on the radially outer side of the permanent magnets 29 isset to a low value in order to attenuate the magnetic shielding effectand so achieve magnetic connection of the magnets 29 and rotor 3.

[0103] Furthermore, deceleration braking is released by rotating themagnet ring 7 z as shown in FIG. 17, because the permanent magnets 10 zof the magnet ring 7 z and the permanent magnets 29 of the magnetic ring27 are magnetically short-circuited. In this case, the magnetism of thepermanent magnets 10 z of the magnet ring 7 z is short-circuited withthe permanent magnets 29 of the magnetic ring 27, which is more easilyconnected therewith than the rotor 3, so magnetic leakage to the rotor 3is suppressed.

[0104] Also, by arranging permanent magnets 10 z in hill/valley fashionin the magnet ring 7 z constructed as shown in FIG. 15, the pole area ofthe permanent magnets 10 z with respect to the inner circumferentialsurface of the magnetic ring 7 z (i.e. the inner circumferential surfaceof the rotor 3) can be made larger than in the case of the type shown inFIG. 12 to FIG. 14, so braking force can be increased.

[0105] A further embodiment is shown in FIG. 18(a), FIG. 18(b) and FIG.19.

[0106] As shown in this Figure, in this embodiment, the rotor 3 is madeof a disk type rather than of the drum type that has been employedhitherto. [0105]. As shown in FIG. 18(a) and FIG. 18(b), this eddycurrent deceleration device 1 b comprises a disk-shaped rotor 44 mountedon a rotary shaft 42 of a power transmission system such as the driveshaft of a vehicle and a stator 45 (source of magnetic force) mounted ona fixed system such as a vehicle transmission arranged opposite therotor 44. Deceleration braking of the vehicle is performed by generatingeddy currents in the rotor 44 by supplying magnetism to the rotor 44from the stator 45 and deceleration braking is released by shielding themagnetism in the stator 45.

[0107] The stator 45 comprises: a hollow ring-shaped casing 46 that ismounted on a fixed system, not shown, and is journaled by bearings 60 ona rotary shaft 42; a first magnet ring 48 that is freely rotatablyaccommodated by means of a bush or bearings 47 in the casing 46 and anactuator (fluid cylinder or the like), not shown, that rotates the firstmagnet ring 48. The first magnet ring 48 comprises a plurality ofpermanent magnets 49 arranged with a prescribed spacing in thecircumferential direction and magnetic members 50 (iron or the like)interposed between the permanent magnets 49. The permanent magnets 49comprise pole faces at both end faces in the circumferential directionand are arranged with poles facing in the circumferential directionbeing of same polarity.

[0108] In addition, there is integrally provided a second magnet ring 51comprising permanent magnets and magnetic members like the permanentmagnets 49 and magnetic members 50 of the first magnet ring 48 arrangedin the casing 46 between the first magnet ring 48 and the rotor 44.Specifically, the second magnet ring 51 comprises a plurality ofpermanent magnets 52 arranged with facing poles in the circumferentialdirection being of the same polarity and mounted with a prescribedspacing in the circumferential direction and magnetic members 53 (ironor like) interposed between the permanent magnets 52. Thepitch/circumferential length of the permanent magnets 49, 52 and themagnetic members 50, 53 of the magnet rings 48, 51 are set to bemutually equal. The magnetic members 50, 53 constitute pole pieces ofthe permanent magnets 49, 52.

[0109] The second magnet ring 51 is constituted in ring shape byconnecting magnetic members 53, 53 formed for example in block shapesandwiching the permanent magnets 52 by means of connecting elements 55that are fixed by means of bolts, screws or other fixing elements 54. Anembodiment of the invention according to claim 1 is constituted byforming these connecting elements 55 of non-magnetic bodies while anembodiment of the invention according to claim 2 is constituted byforming the connecting elements 55 of magnetic bodies. This is because,in the latter case, the second magnet ring 51 is in a condition in whichpermanent magnets 52 are embedded in a magnetic body and so constitutesa magnetic ring according to the invention of claim 2.

[0110] The operation of this embodiment will now be described (in thecase in which the connecting elements 55 are formed of non-magneticbodies).

[0111] When deceleration braking of this eddy current decelerationdevice 1 b is turned off, as shown in FIG. 18(a), the permanent magnets49 of the first magnet ring 48 and the permanent magnets 52 of thesecond magnet ring 51 are put in a phase in which they are adjacent toopposite polarity poles, by rotating the first magnet ring 48 by meansof an actuator, not shown. When this is done, the permanent magnets 49of the first magnet ring 48 and the permanent magnets 52 of the secondmagnet ring 51 are mutually magnetically short-circuited to constitute ashielding magnetic circuit 56, with the result that no eddy currents aregenerated in the rotor 44 and deceleration braking does not occur.

[0112] In contrast, when deceleration braking is turned on, as shown inFIG. 19, the permanent magnets 49 of the first magnet ring 48 and thepermanent magnets 52 of the second magnet ring 51 are put in a phase inwhich identical polarity poles are adjacent to each other, by rotatingthe first magnet ring 48. Magnetic circuits 57, 58 are then constitutedby the permanent magnets 49, 52 of the first and second magnet rings 48,51 and the rotor 44, generating eddy currents in the rotor 44 andthereby performing deceleration braking of the vehicle.

[0113] During deceleration braking shown in FIG. 19, the respectivepermanent magnets 49, 52 of the first and second magnet rings 48, 51 arein a condition in which they are lined up in pairs with identicalpolarity poles along the radial direction, so strong magnetic force isexhibited by the sets respectively constituted by these pairs ofpermanent magnets. Accordingly, a strong braking force such as would beproduced by the magnetic force of a permanent magnet of substantiallythe length of two such permanent magnets is obtained.

[0114] Also, the respective permanent magnets 49, 52 of the first andsecond magnet rings 48, 51 can be separately magnetized in therespective first magnet ring 48 and second magnet ring 51 afterassembly, with the permanent magnets 49, 52 when this magnetization isperformed being of length half the length of the sets described aboveconstituted by two magnets. Consequently, even if the spacing betweenadjacent permanent magnets 49 and 49 or 52 and 52 in the circumferentialdirection is reduced, ample magnetization can still be achieved. Brakingforce is therefore improved.

[0115] It should be noted that, if the connecting elements 55 are formedof magnetic bodies, the magnetic flux when braking is turned on/off isas shown in FIG. 8 and FIG. 9. That is, in this case, in order to turnbraking off, it suffices to create offset of the first magnet ring 48 byan amount smaller than 1 pitch (for example ⅓ pitch or ⅔ pitch) (notshown in the drawings).

[0116] A further embodiment is illustrated in FIG. 20(a), FIG. 20(b) andFIG. 21.

[0117] As shown in these Figures, the eddy current deceleration device 1c according to this embodiment differs from the previous embodiment onlyin that two rotors 44 according to the previous embodiment are employedand the stator 45 is arranged therebetween. Like components aretherefore given the same reference symbols and further descriptionthereof is omitted.

[0118] In this embodiment also, braking is turned off by rotating thefirst magnet ring 48 as shown in FIG. 20(a) by means of the actuator andbraking is turned on by rotating the first magnetic ring 48 as shown inFIG. 21. In this embodiment also, an embodiment of the inventionaccording to claim 1 is obtained if the connecting elements 55 areformed of non-magnetic bodies and an embodiment of the inventionaccording to claim 2 is obtained if the connecting elements are formedof magnetic bodies.

[0119] A further embodiment is illustrated in FIG. 22 and FIG. 23.

[0120] As shown in the drawings, an eddy current deceleration device idaccording to this embodiment is of substantially the same constructionas the eddy current deceleration device 1 c according to the firstembodiment illustrated in FIG. 20(a), FIG. 20(b) and FIG. 21 and differsonly in regard to the construction of the first magnet ring 48, which isaccommodated in the casing 46 of the stator 45. Like components aretherefore given the same reference symbols and further descriptionthereof is omitted, only the points of difference being described.

[0121] As shown in FIG. 22 and FIG. 23, this first magnet ring 48 acomprises a plurality of permanent magnets 49 a arranged with aprescribed spacing in the circumferential direction with non-magneticmembers 50 a provided between the permanent magnets 49 a. The permanentmagnets 49 a have poles at the opposite ends in the axial direction andare arranged with the polarities of adjacent magnets being opposite.

[0122] In this embodiment also, braking is turned off by rotating thefirst magnet ring 48 a as shown in FIG. 22 by means of an actuator andbraking is turned on by rotating the first magnet ring 48 a as shown inFIG. 23.

[0123] It should be noted that, although, in each of the aboveembodiments, a type was described in which the first magnet ring wasrotated without rotating the second magnet ring, it would, contrariwise,be possible to rotate the second magnet ring without rotating the firstmagnet ring, or indeed to rotate both magnet rings.

[0124] An embodiment of the invention according to claim 5 will now bedescribed

[0125]FIG. 24 is a front cross-sectional view of an eddy currentdeceleration device according to an embodiment in which decelerationbraking is achieved by applying magnetism to the rotor, seen from thedirection of the end of the drive shaft; FIG. 25 is a frontcross-sectional view of an eddy current deceleration device whendeceleration braking is turned OFF and FIG. 26 is a lateralcross-sectional view of an eddy current deceleration device seen fromoutside the rotor in the radial direction.

[0126] As shown in FIG. 26, this eddy current deceleration device 101comprises a drum-shaped rotor 103 mounted on a rotary shaft 102 of apower transmission system such as the drive shaft of a vehicle and astator (source of magnetic force) 104 mounted on a fixed system (notshown) such as a vehicle transmission arranged along the innercircumference of a rotor 103. Deceleration braking of the rotary shaft102 is achieved by generating eddy currents in the rotor 103 bysupplying magnetism to the rotor 103 from the stator 104 anddeceleration braking is released by shielding the magnetism in thestator 104.

[0127] The stator 104 comprises a casing 105 formed in hollow shapesupported on a fixed system, a magnet ring 108 having a plurality ofpermanent magnets 107 accommodated so as to be freely rotatable about acommon axis by means of a bush 106 in the casing 105, a magnetic ring110 having a plurality of permanent magnets 109 integrally provided inan outer circumferential portion of the casing 105 so as to bepositioned between the magnet ring 108 and the rotor 103 and an actuator(fluid cylinder or the like) 111 used to rotate the magnet ring 108.

[0128] As shown in FIG. 24, the magnet ring 108 comprises a support ring112 made of a magnetic body (laminated body of electromagnetic steelsheet or iron block member or the like) engaged with the outercircumference of the bush 106 and a plurality of permanent magnets 107arranged facing the rotor 103 mounted at a prescribed pitch (spacing) inthe circumferential direction at the outer circumference of the supportring 112.

[0129] Specifically, the permanent magnets 107 are arranged with theirrespective poles directed radially and alternately inverted in thecircumferential direction. That is, the permanent magnets 107 haverespective poles at their outside ends and inside ends in the radialdirection and adjacent poles in the circumferential direction arearranged to have alternate polarity.

[0130] Also, respective spaces 113 are formed between permanent magnets107 that are adjacent in the circumferential direction, so thatmagnetism that is generated from the permanent magnets 107 is notshort-circuited.

[0131] The magnetic ring 110 is constituted by embedding a plurality ofpermanent magnets 109 at a prescribed pitch (spacing) in thecircumferential direction in the interior of an annular magnetic member114 made of a magnetic body (for example, a soft magnetic member such asan iron block member or laminated electromagnetic steel sheet); polepieces are formed by the magnetic members 114. The permanent magnets 109are embedded so as to be held in particular covering the face on theside of the rotor 103.

[0132] The permanent magnets 109 of the magnetic ring 110 are arrangedto be of the same number as the permanent magnets 107 of the magnet ring108 and are respectively in one-to-one correspondence with the permanentmagnets 107 of the magnet ring 108. The relative phases of the mutuallycorresponding permanent magnets 107, 109 can be varied in common byrotating the magnet ring 108.

[0133] Also, the permanent magnets 109 of the magnetic ring 110 arearranged so as to emit magnetism of the same intensity as the respectivepermanent magnets 107 of the magnet ring 108 and are arranged such thatrespective facing poles thereof in the circumferential direction are ofsame polarity.

[0134] The magnetic members 114 have raised portions 115 projecting onthe side of the rotor 103 (radially outwards) between the permanentmagnets 109 so as to efficiently transmit the magnetism emitted from themagnetic ring 110 and magnet ring 108 towards the rotor 103 duringdeceleration braking. Also, the covering section 116 that covers theportions of the magnetic members 114 facing the rotor 103 is formed ofsufficiently small thickness to be isolated from the rotor 103.

[0135] An actuator 111 is formed so as to be able, by rotating themagnet ring 108, to set one of a phase (braking position: FIG. 24) inwhich permanent magnets 107, of the permanent magnets 107 of the magnetring 108, with faces (poles) which are of the same polarity as theaforesaid poles facing radially outwards (towards the rotor 103) aresandwiched at equal intervals between adjacent permanent magnets 109with identical polarity poles facing in the circumferential direction ofthe magnetic ring 110, and a phase (non-braking position: FIG. 25) inwhich permanent magnets 107, of the permanent magnets 107 of the magnetring 108, in which opposite polarity poles face radially outwards aresandwiched therebetween at equal intervals.

[0136] Specifically, the actuator 111, by rotating the magnet ring 108,sets one of a phase (braking position: FIG. 24) in which permanentmagnets 107, of the permanent magnets 107 of the magnet ring 108, whichare of the same polarity as the permanent magnets 109 are sandwiched theaforesaid magnetic members 114, face the magnetic members 114 betweenthe permanent magnets 109 of the magnetic ring 110, and a phase(non-braking position: FIG. 25) in which permanent magnets 107 which areof opposite polarity face these magnetic members 114.

[0137] Next, the operation will be described.

[0138] When deceleration braking of the eddy current deceleration device101 is turned on, the magnet ring 108 is rotated by the actuator 111shown in FIG. 26 so that the magnet ring 108 is put in a phase wherein,as shown in FIG. 24, permanent magnets 107, of the permanent magnets 107of the magnet ring 108, with faces which are of the same polarity as theaforesaid poles facing radially outwards are sandwiched at equalintervals between adjacent permanent magnets 109 with identical polaritypoles facing in the circumferential direction of the magnetic ring 110.That is, the magnet ring 108 is put into the braking position describedabove.

[0139] When this happens, the magnetism that is emitted from thepermanent magnets 107, 109 of the magnetic ring 110 and magnet ring 108is transmitted to the rotor 103 through the raised portions 115 of themagnetic ring 110 under mutual repulsion, thereby constituting magneticcircuits 117, 118 respectively connecting the stator 104 and the rotor103. Eddy currents are therefore generated in the rotor 103, producingdeceleration braking of the rotary shaft 102.

[0140] Since the magnetism respectively generated from the permanentmagnets 107, 109 of the magnet ring 108 and magnetic ring 110 is thentransmitted to the rotor 103, the magnetism density that is transmittedto the rotor 103 is much larger than in the case of a prior art typeeddy current deceleration device, so strong braking force is obtained.

[0141] In contrast, when deceleration braking is turned off, the magnetring 108 is rotated as shown in FIG. 25, in which the magnet ring 108 isput into a phase in which permanent magnets, of the permanent magnets107 of the magnet ring 108, that face opposite polarity poles in theradially outwards direction, are sandwiched at equal intervals betweenadjacent permanent magnets 109 with identical polarity poles facing inthe circumferential direction of the magnetic ring 110. When this isdone, the permanent magnets 107 of the magnet ring 108 and the permanentmagnets 109 of the magnetic ring 110 are mutually magneticallyshort-circuited, establishing shielding magnetic circuits 119.

[0142] Since permanent magnets 107, 109 which are of substantially thesame strength are mutually magnetically short-circuited, there is nomagnetic leakage to the rotor 103, so generation of dragging torque canbe prevented. Also, in particular, since the covering section 116 of themagnetic ring 110 is amply isolated from the rotor 103, any slightamount of magnetism leaking from the permanent magnets 109 ismagnetically short-circuited through the covering section 116 withoutbeing transmitted to the rotor 103.

[0143] In this way, an eddy current deceleration device 101 isconstituted comprising: a rotor 103 that is mounted on a rotary shaft102; a plurality of permanent magnets 107 that are arranged facing therotor 103, their magnetic poles being arranged in alternately invertedfashion at a prescribed pitch in the circumferential direction andfacing the rotor 103 (directed radially) and a magnet ring 108 havingmagnetic members 114 that magnetically link magnetic poles, of themagnetic poles of these permanent magnets 107, that face away from therotor 103 (radially inwards); and a magnetic ring 110 arranged betweenthe magnet ring 108 and rotor 103 and having a plurality of permanentmagnets 109 that are arranged at a prescribed pitch in thecircumferential direction and with facing poles in the circumferentialdirection being of same polarity and magnetic members 114 that holdthese permanent magnets 109, covering the side thereof nearest the rotor103; at least one of the magnet ring 108 and magnetic ring 110 beingfreely rotatable. The braking force can therefore be increased(approximately doubled per unit circumferential length) and generationof dragging torque can be prevented.

[0144] It should be noted that, although, in the case of the magnet ring108, spaces 113 were formed between the permanent magnets 107 thereof,there is no restriction to this, and the permanent magnets 107 could bemagnetically separated by providing non-magnetic bodies (not shown) offor example austenitic stainless steel therebetween.

[0145] Also, although it was arranged for the magnet ring 108 to berotated by the actuator 111, it could be arranged for the magnetic ring110 to be rotated instead of the magnet ring 108, or indeed for both themagnet ring 108 and magnetic ring 110 to be rotated.

[0146] Furthermore, although the stator 104 was arranged along the innercircumference of the rotor 103, there is no restriction to this and astator 121 could be placed along the outer circumferential side of arotor 120 as shown in FIG. 32, so long as it lies along the rotor 103.

[0147] Also, as shown in FIG. 33, a stator 123 could be placed along theshaft side of a rotor 122. In this case, a magnetic ring 126 could bearranged between a magnet ring 124 and rotor 122, with permanent magnets125 of the magnet ring 124 facing the rotor 122, in the same way as inthe embodiment described above. The poles of the permanent magnets 125of the magnet ring 124 could be directed in the axial direction.

[0148] Next, a further embodiment will be described of a case in whichthe magnetic ring 110 cannot be made sufficiently thick in the radialdirection. The construction of the magnetic ring 110 and the actuator111 described above is modified but the rest of the construction is thesame apart from some adjustment regarding size, so the same referencesymbols are attached and further description thereof is omitted.

[0149]FIG. 27 is a front cross-sectional view seen from the shaft end ofthe rotary shaft 2 of an eddy current deceleration device 140 accordingto the present embodiment, in which deceleration braking is achieved byapplying magnetism to the rotor 103.

[0150] As shown in FIG. 27, a magnetic ring 141 is constituted byembedding with the same arrangement permanent magnets 143 of smallerthickness in the radial direction than the permanent magnets 109described above, in the interior of magnetic members 142 formed ofsmaller thickness in the radial direction than the magnetic members 114described above.

[0151] The magnetic members 142 are provided with raised sections 144projecting towards the rotor 103 in the same way as described above anda covering section 145 is formed of sufficiently small thickness.

[0152] Also, since the permanent magnets 143 of the magnetic ring 141are smaller than those described above, their magnetic force isrespectively weaker than that of the permanent magnets 107 of the magnetring 108.

[0153] An actuator (not shown) is formed so as to rotate the magnet ring108 so as to set the magnet ring 108 in one of a phase (brakingposition: FIG. 27) in which the permanent magnets 107, of the permanentmagnets 107 of the magnet ring 108, have their faces which are of thesame polarity as the aforementioned poles and that are directed towardsthe rotor 103 are sandwiched at equal intervals between the permanentmagnets 143 of the magnet ring 141, which are adjacent and whereofidentical polarity poles face each other in the circumferentialdirection, and a phase (non-braking position: FIG. 28) in which themagnet ring 108 is offset with a pitch of substantially ⅔ from thisphase in the circumferential direction.

[0154] That is, by rotating the aforesaid magnet ring 108, the actuatorselects one of a phase (braking position: FIG. 27) in which permanentmagnets 107, of the permanent magnets 107 of the magnet ring 108, thatare of the same polarity as the permanent magnets 143 sandwiching theaforesaid magnetic members 142, are directed towards the magneticmembers 142 between the permanent magnets 143 of the magnetic ring 141and a phase (non-braking position: FIG. 28) that is offset with a pitchof substantially ⅔ in the circumferential direction from this brakingposition.

[0155] Next, the operation of this embodiment will be described.

[0156] When deceleration braking of the eddy current deceleration device140 is turned on, the magnet ring 108 is rotated by the actuator so thatthe magnet ring 108 is in a phase such that the permanent magnets 107,of the permanent magnets 107 of the magnet ring 108, whose faces, thatare of the same polarity as the aforesaid poles, are directed radiallyoutwards (towards the rotor 103), are sandwiched at equal intervalsbetween the permanent magnets 143 of the magnetic ring 141, which areadjacent and whereof identical polarity poles face each other in thecircumferential direction, as shown in FIG. 27. That is, the magnet ring108 is put into a braking position.

[0157] When this happens, the magnetism that is emitted from thepermanent magnets 143, 107 of the magnetic ring 141 and the magnet ring108 is transmitted to the rotor 103 through the raised sections 144 ofthe magnetic ring 141 while under mutual repulsion, thereby constitutingmagnetic circuits 147, 148 respectively connecting the stator 146 androtor 103. Eddy currents are therefore generated in the rotor 103, as aresult of which the rotary shaft 102 is subjected to decelerationbraking.

[0158] Contrariwise, when deceleration braking of the eddy currentdeceleration device 140 is turned off, the magnet ring 108 is rotated asshown in FIG. 28 so as to put the magnet ring 128 in a phase offset witha pitch of substantially ⅔ in the circumferential direction from thebraking position. That is, the magnet ring 108 is put into a non-brakingposition. When this happens, a first shielding magnetic circuit 149 isconstituted between the permanent magnets 107 of the magnet ring 108 andthe permanent magnets 143 of the magnetic ring 141 by mutual magneticshort-circuiting of the permanent magnets 107 of the magnet ring 108 andthe permanent magnets 143 of the magnetic ring 141 and a secondshielding magnetic circuit 150 is constituted between the permanentmagnets 107 of the magnet ring 108 and the magnetic members 142 of themagnetic ring 141.

[0159] Thanks to the magnetic short-circuiting, achieved by theconstruction of a second shielding magnetic circuit 150 between themagnetic members 142 of the magnetic ring 141, of any magnetism emittedfrom the permanent magnets 107 of the magnet ring 108 that is notmagnetically short-circuited by the permanent magnets 143 of themagnetic ring 141, none can leak to the rotor 103 and generation ofdragging torque can be prevented.

[0160] Also, since the permanent magnets 107 of the magnet ring 108 areformed with ample length in the circumferential direction such as toextend in the circumferential direction beyond the position of thepermanent magnets 143 of the magnetic ring 141 when the magnetic ring108 is set in the non-braking position, the second shielding magneticcircuit 150 can be constituted in an increased thickness portion(portion where there are no permanent magnets 143) of the magneticmembers 142, that is not likely to be magnetically saturated.

[0161] Thus, thanks to the provision of an actuator that sets, byrotating the magnet ring 108, one of a phase (braking position) in whichpermanent magnets 107, of the permanent magnets 107 of the magnet ring108, whose faces which are of the same polarity as the aforesaid polesare directed towards the rotor 103 are sandwiched at equal intervalsbetween permanent magnets 143 that are adjacent and whose identicalpolarity poles face each other in the circumferential direction of themagnetic ring 141 and a phase (non-braking position) wherein the magnetring 108 and magnetic ring 141 are offset by a pitch of substantially ⅔in the circumferential direction from the foregoing phase, even if thepermanent magnets 143 of the magnetic ring 141 are set to have a weakermagnetic force than the permanent magnets 107 of the magnet ring 108,generation of dragging torque can be prevented and braking force can beconsiderably improved.

[0162] It should be noted that although it is preferable from the pointof view of ease of magnetic saturation of the vicinity of the permanentmagnets 143 of the magnetic ring 141 that the non-braking positionshould be in a phase offset by a pitch of substantially ⅔ in thecircumferential direction from the braking position, there is norestriction to this. So long as this phase (non-braking position) isoffset by a prescribed rotational width that exceeds a pitch of ½ in thecircumferential direction but is less than 1 pitch from the brakingposition, a second shielding magnetic circuit 150 can be constituted andgeneration of dragging torque can be prevented.

[0163] Also, although the magnetic ring 141 was constituted by embeddinga plurality of permanent magnets 143 in an annular magnetic member 142,there is no restriction to this.

[0164] For example, as shown in FIG. 29, the magnetic ring 141 could beconstituted by providing a plurality of magnetic blocks 160 constitutingpole pieces and formed in arcuate shape and connecting elements 161connecting the ends in the circumferential direction of these magneticblocks 160 while holding the permanent magnets 143.

[0165] Specifically, the magnetic blocks 160 may be constituted bymagnetic bodies (for example soft magnetic members such as iron orlaminated electromagnetic steel sheet) formed in block shape. Theconnecting elements 161 may comprise outer circumferential members 162for structurally connecting the outer circumferential sides of the endsin the circumferential direction of the magnetic blocks 160 and innercircumferential connecting members 163 for structurally connecting theinner circumferential sides of these ends, the permanent magnets 143being held or fixed by being sandwiched between the innercircumferential connecting members 163 and the outer circumferentialconnecting members 162.

[0166] The external circumferential collecting members 162 and internalcircumferential connecting members 163 may be of a shape such as plateshape, net shape or rod shape elongate in the circumferential directioncapable of connecting the magnetic blocks 160 with each other and offixing the permanent magnets 143 and may be mounted on the magneticblocks 160 using fixing metal elements 162 such as bolts or screws.

[0167] The outer circumferential connecting members 162 and innercircumferential connecting members 163 are preferably formed ofnon-magnetic material such as aluminum or stainless steel but could beformed of magnetic material (for example soft magnetic material such aselectromagnetic steel sheet).

[0168] The end faces of the magnetic blocks 160 facing the axialdirection (longitudinal direction) may be suitably formed with boltholes 165 for fixing in the casing 105 of the stator 104.

[0169] Also, as shown in FIG. 30, the magnetic members 171 of themagnetic ring 170 may be formed in annular shape and may be providedwith embedding holes 173 for fixing permanent magnets 172 by embeddingthe permanent magnets 172 therein. In this case, the embedding holes 173may be formed on the radially inwards side of the magnetic members 171or may be formed, from apertures 175 formed in the inner circumferentialface 174 of the magnetic member 171, with width increasing in taperedfashion in the inwards direction (radially outwards direction). Thepermanent magnets 172 can thus easily be prevented from falling out fromthe magnetic member 171.

[0170] Also, in addition, as shown in FIG. 31, the embedding holes 180may be formed with increasing width in stepwise fashion from apertures183 formed in the inner circumferential surface 182 of the magneticmembers 181 in the inwards direction (radially outwards direction), theessential feature being that the width of these embedding holes isreduced at their apertures.

What is claimed is:
 1. An eddy current deceleration device comprising: arotor mounted on a rotary shaft; a first magnet ring arranged facing therotor and comprising a plurality of permanent magnets that are arrangedwith a prescribed spacing in the circumferential direction and such thatthe poles thereof facing in the circumferential direction are of a samepolarity, and magnetic members interposed between these permanentmagnets; and a second magnet ring arranged between this first magnetring and the rotor and comprising permanent magnets and magnetic memberssimilar to those of the first magnet ring; at least one of the first andsecond magnet rings being freely rotatable.
 2. An eddy currentdeceleration device comprising: a rotor mounted on a rotary shaft; amagnet ring arranged facing this rotor and comprising a plurality ofpermanent magnets that are arranged at a prescribed pitch in thecircumferential direction and such that the polarities of their polesfacing said rotor are alternately inverted, and magnetic members forconnecting the magnetic poles, of these permanent magnets, that face theopposite side of said rotor; and a magnetic ring arranged between thismagnet ring and the rotor and comprising a plurality of permanentmagnets that are arranged at a prescribed pitch in the circumferentialdirection and such that the poles thereof facing in the circumferentialdirection are of a same polarity, and magnetic members that hold thesepermanent magnets; at least one of the magnet ring and magnetic ringbeing freely rotatable.
 3. The eddy current deceleration deviceaccording to claim 1 or 2 wherein said rotor comprises a drum body fixedto the rotary shaft.
 4. The eddy current deceleration device accordingto claim 1 or 2 wherein said rotor comprises a disk body fixed to therotary shaft.
 5. The eddy current deceleration device according to claim2 comprising an actuator that rotates at least one of said magnet ringand magnetic ring and that sets the relative position of the magnet ringand magnetic ring in one of a braking position, in which permanentmagnets of the permanent magnets of the magnet ring that are of the samepolarity as the permanent magnets sandwiching the magnetic members aredirected towards magnetic members between the permanent magnets of themagnetic ring, and a non-braking position in which the magnet ring andthe magnetic ring are offset by a prescribed rotational width exceeding½ pitch but less than 1 pitch in the circumferential direction from thisbraking position.
 6. The eddy current deceleration device according toclaim 5 wherein said non-braking position is set in a position offset bysubstantially ⅔ pitch in the circumferential direction from said brakingposition.
 7. The eddy current deceleration device according to any ofclaims 2, 5 and 6 wherein said magnetic ring comprises a plurality ofmagnetic blocks formed in arcuate shape and connecting elements thatconnect the ends in the circumferential direction of these magneticblocks, while holding the permanent magnets.
 8. The eddy currentdeceleration device according to any of claims 2, 5, and 6 wherein amagnetic member of said magnetic ring is formed in annular shape and isprovided with embedding holes so that said permanent magnets areembedded and fixed in these holes.